Method of recovering copper from its ores.



PATENTED MAY 16, 1905.

M. WILGOX. METHOD OF REGOVBRING COPPER FROM ITS 0112s.

LPPLIOA'IION FILED MAB. 6, 1906.

2 SHEETS-SHEET 1.

111790.238. PATENTBD MAY1'6,1905. H. M, WILGOX.

METHOD OF REGOVERING COPPER FROM ITS vORES.

' nrmouxon IILED MAR. e, 1905.

2 sums-81mm 2:

I N0. 790,238. I latented. May 16, 1905.

UNITED STATES PATENT OFFICE.

HENRY M. VVILCOX, OF CHICAGO, ILLINOIS, ASSIGNOR TO ESMERALDA COPPER PRECIPITATING COMPANY, OF CHICAGO, ILLINOIS, A CORPO- RATION.

-METHOD OFRECOVERING COPPER FROM ITS ORES.

SPECIFICATION formingpart of Letters Patent No. 790,238, dated May 16, 1905.

Application filed March 6, 1905. Serial No. 248,488. E

M A. Jar-MI.

T whom? it y Concern/1 On the 'drawings, Figure 1 shows a dia- Be it known that I, HENRY M. WILCOX, a grammatic view of the main details of the citizen of the United States, residing at Chiplant in elevation. Fig. 1 is a diagrammatic cago, in the county of Cook, State of Illinois, view of the precipitatingboiler in section. 5 have invented certain new and useful Improve- Fig. 2 is a like view of the leaching-barrels. ments in Methods of Recovering Copper from v The selected ore having been crushed and its Ores, of which the following is hereby deground, as usual, is digested in rotating barclared to be a full, clear, and exact description. rel a with dilute sulfuric acid of about seven The invention aims to obtain copper from per cent. strength until the reaction with the 1 its low-grade ores in metallic state by use of copper in the ore is complete and the solusulfur dioxid acting as a precipitant to throw tion becomes neutral say at the end of sevdown the copper under requisite conditions. eral hours. Test shows the finished solution I from cupric-sulfate solution, ordinarily conto be of about 1.136 specific gravity with some stituting the leach liquor, the charge being 5.01 per cent. of metallic copper present I 5 treated under proper heat and pressure in a therein. Any increase in the strength of the close vessel left with certain extent of free acid will correspondingly increase the conspace therein suited to cause the copper to tent of copper; but the point of saturation for separate out practically in pure state withthe cupric-sulfate solution is soon attained, 5 scarcely a trace of its oxid or sulfite present when the metallic copper present ranges, say,

20 to impair the product. i at about seven per cent., (7 Regard being Heretofore the use of sulfur dioxid as a had to the lower reach of temperature to ensue reagent for recovery of copper from cupricin course of treatment later on, it is obviously sulfate solution has been proposed; but the useless to saturate the cupric solution only to conditions of treatment laid down for the lose again the excess salts when the solution 25 prior practice fail to derive the copper praccools down or chills. Hence the acid strength tically pure, the result instead being merely may for economy be fairly fixed at about seven to produce a large amount of copper oxid or per cent, (7 %,)as already stated. The specific sulfite'with more or less of granular metal gravity of the solution varies somewhat in intermixed. The percentage of metal recovkeeping with the quantity ofrefuse salts,

3o ered is apt to vary widely for successive such as iron or the like. After leaching is charges treated, although in no event is the over the resultant cupric-sulfate solution in' yield of much moment on comparison with hot state is drawn from barrel (0 into the elethe intermingled oxid or sulfite which goes vated settling-tank I), while the refuse ore redown at the same time. moved from barrel (6 is washed in tank 0 to 3 5 Under the new treatment recovery of the recover the remnant of sulfate solution. Havcopper is had in isolated state nearly if not ing run the dilute wash liquor into neutraliz wholly free from oxid or sulfite, thus for the ing-tank cl for reuse, the refuse ore is taken first time rendering the use of sulfur dioxid out of tank 0 and cast away upon the dump. an'economic precipitant When metallic copper The hot solution of cupric sulfate present in 40 is the product to be obtained. settling-tank b may be treated there by air- While the present invention does not deblast to throw down any excess of iron salts pend for its success upon any special form of or other impurities if present in quantity plant or of precipitating vessel,experience has say five per cent. or oversufficient to prove shown that an apparatus such as illustrated a nuisance later on. Should the iron or other 45 by the drawings that accompany may be used impurities be present only in minor quantity, to advantage in dealing with copper carbon V they can be ignored. After the precipitates ate or, oxid ores of low grade. settle away the clear solution of cupric sulfate is allowed to run from tank 6, through cooler 6, into the topmost absorption-vat f.

Cooler 0 may be a simple'pipe rebent in series form and submerged in the water vessel. Absorption-vatfilike the others of the set viz., f -is closed at top, but near the base is furnished with a perforated false bottom to sustain a charge of crushed copper ore, ordinarily such as the'solution itself comes from. At bottom the companion vats f f f are united by suitable pipes, through which the solution of cupric sulfate is tapped off and descends from vat to vat at intervals, say, of about every two hours. The ore found in such vat acts to take upany free acid, so that the sulfate solution is kept neutral while absorption by it of the sulfur-dioxid gas proceeds. A sufficient supply of sulfur dioxid can be had by burning sulfur or 'sulfid ore in some suitable furnace, from which the evolved gases are drawn by aid of an exhaust-pump, with coolingcoil between to chill the gasesbefore passing through the pump. After leaving the pump the gas is delivered by pipe g directly into the lower absorption-vat f at a point beneath the false bottom thereof. The dioXid gas bubbles up through the charge and passes on from vat to vat by pipes g g until it is completely absorbed, the associated nitrogen finally emerging through exit 9 at vat f to the air.

The cupric-sulfate solution greedily dissolves the dioxid gas passing through it, so that the charge in lower vat f after an hour or so becomes completely saturated." It can contain no more and is at once drawn off into storage-tankc' in readiness for precipitation treatment. The absorption of the dioxid gas is attended by a marked decline in temperature,which must result in turn in fouling the vats and connecting-pipes with a deposit of cupric sulfate passing out of solution if in eX- cess at thelow degree of heat.

The charge of cupric sulfate saturated with sulfur'dioxid stands at about 60 Fahrenheit and is found to contain: copper, 4.7 8 per cent.'; combined sulfuric acid, 7.22 per cent., and sulfur dioXid, 2.89 per cent., with a specific gravity 1.147 for the solution. The charge passes from storage-tank 2' into the "precipitati'ng vessel 7b, which is made in any convenient form, here shown as a simple upright flue-boiler'with the liquid circulating in its fines is, while the steam for heating the charge surrounds the fines between the boiler-head plates Z.

According to practice distinctive of the invention, care must be taken not to overfill the boiler'with the charge. Speaking roughly, a space representing about one-tenth of the total content of vessel must be left vacant. When reaction occurs at high heat, the sul- .fur dioXid is energetically driven off in gaseous state. Space ample enough to freely receive the gas must be left within the vessel, so that although still held the sulfur dioxid is no longer detained inthe body of liquid to impair the success of the reaction.

Were the tank filled practically full, experience shows that the copper goes down largely as an oxid or sulfite, and it is only by providing ample space beforehand for free exit of the sulfur dioxid from the body of liquid at the critical reaction stage, lasting but a minute or so, that the copper is obtained in metallic state with scarcely a trace of oxid or sullite present.

Having filled the boiler to the desired extent, the charge is simply heated in the closed vessel until it attainsa proper temperature a. 9., 233 Fahrenheitat which juncture it is under about one hundred and live pounds pressure. The reaction proceeds quickly with marked energy, the copper separating out and accumulating at the bottom, while the sulfur dioxid passes off into the confined space at top.

Once the reaction is finished a suitable cock is opened at top to release the sulfur dioxid, which can be led away to some storage-receptacle for reuse. After the gas is vented it is simply requisite to draw off the spent liquor and thereafter remove and wash the copper precipitate preliminary to casting it into ingot form for the market.

In practice metallic copper representing 44.81 per cent. of the total copper present in solution has been obtained, showing 99.7 per cent. pure, while the spent liquor remains still rich in copper, analysis of the solution at specific gravity 1.143 disclosing copper, 2.87 per cent. combined sulfuric acid, 410 per cent; free sulfuric acid, 9.60 per cent., with specific gravity 1.143 for the liquid.

The spent solution can be returned to neutralizing-tank c and be dosed there with quicklime or like reagent sufiicient in quantity to reduce the percentage of free sulfuric acid, it found necessary. The clear liquor passes into rotating barrel (1 as desired, to become the solvent for another batch of ground ore. Instead of neutralizing the spent solution a part of it can be diluted with water to reduce the percentage'of free sulfuric acid, so as'to render it lit for the leach liquor, while the remaining part is evaporated in open vats for recovery of the crystallized salts of copper.

While the ordinary practice contemplates the use of dilute sulfuric acid for the leaching agent, it is entirely feasible to employ sulfur dioxid in its place, this being introduced into the revolving barrel a in liquid or gaseous form until the water present with the crushed ore is fully saturated.

The sulfur dioxid attacks the copper, iron, &c., present in the ore and may need to be replenished by further supply as the reaction proceeds. After leaving the barrel or even while there a minor percentage of sulfuric acid can be added to advantage sufficient to avert any premature deposit of copper oxid that might otherwise occur once the sulfur dioxid in solution should become deficient in quantity requisite, to hold the copper in solution.

Owing to the heat of reaction the sulfite-sulfate solution of copper on withdrawal from, barrel a should be chilled down, as before, by

aid of cooler c after leaving the settling and purifying tank 6 in passage direct to storagetank 71. Sliglit additions of sulfuric acid may occur at both tanks should the sulfur dioxid prove insufficient to stop premature deposit of the copper in oXid state. According to the modified practice the copper solution is not required to pass through absorption-vats f, f, and f since the sulfur dioXid has already been introduced at the outset as a dissolving agent.

By either procedure copper sulfate is found present in solution associated with practically a saturated solution of sulfur dioxid in readiaccording to the knowledge of persons skilled Variations therefrom may occur in the art without essential departure from the scope of the invention.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is

1. The process of recovering copper from its ores by the wet way, which consists in leaching the ore with suitable reagent to form cupric-sulfate solution, dosing the solution with sulfur dioXid, and thereafter, in a closed vessel having proper vacant space left therein, subjecting said solution to heat and pressure, suited for precipitation of the copper in metallic form while the sulfur dioxid is free to escape from the liquid into the confined space in such vessel provided, to perfect the reaction, substantially as described.

2. Theprocess of recovering copper from its ores by the wet way, which consists in leaching the ore with suitable reagent to form cupric-sulfate solution, blowing air through the hot solution to remove iron or other impurities, dosing the solution with sulfur dioxid, practically to the point of saturation, and thereafter, in a closed vessel having proper vacant space left therein, subjecting said solution to heat and pressure, suited for precipitation of the copper in metallic form while the sulfur dioxid is free to escape from the liquid into the confined space in such vessel provided, to perfect the reaction, substantially as described.

HENRY M. WILCOX.

Witnesses:

RICHARD H. SALTER, J OSEPH G. SPENCER. 

